My levels are perfect.. why?

[reefermadness]

Alk is low, ca a little high and mg is fine. Why would you want mg higher than 1300ppm that is already as high or slightly higher than natural seawater.

Also 20ppm nitrate is perfect for an lps tank but I would stick to you water change schedule and hold it there. If it starts dropping really low just feed more... lps love food and water changes will let you add more.

As far as major element utilization I believe it's possible you tank is just not using as much as you expected.